Is it true that bats cannot see? If they cannot see, then how do they fly around safely without hitting trees and other animals?

It is not true bats cannot see. They can see but in the dark or at a night. To fly around they use a technique called echolocation. Let’s divide this world into parts-echo+location. The echo as you know is the sound that returns when you shout. So bats make noises and wait for them to come back. if the sound doesn’t hit any object and doesn’t come back, it means it is safe for the bat to fly forward. That is how they locate their way. They can also tell from how quickly the sound bounces back that how far an object is!